The invention pertains to drilling and rock excavation as well as petroleum, oil and gas drilling, whether off-shore or terrestrial. The invention also relates to off-shore mineral exploration.
Drilling and rock excavation represent a significant segment of the total mining system, and the yearly drilling costs for copper, iron, lead, zinc, silver, gold and crushed and dimension stone in the U.S. are about 1.5 billion dollars.
Bit costs represents about 600 million dollars or 40% of the total costs.
Productivity of drilling is normally improved by increasing the applied mechanical stress in order to increase the drilling rate; however, such increases in applied mechanical stress causes catastrophic bit or blade wear and reduces its useful drilling life.
Therefore, significant savings could be realized in general drilling costs if a method is devised which allows increased drilling rates at constant applied mechanical stress during the drilling, but prevents bit or blade wear. In particular, these savings would be reflected in the drilling and rock excavation areas as well as in petroleum, oil, gas and mineral drilling exploration.
Enhanced drilling rates have been previously observed in the laboratory by other researchers on a sporadic or on-and-off basis and are summarized by P.J. Watson and W.H. Engelmann, in an article entitled Chemically Enhanced Drilling: An Annotated Tabulation of Published Results. BuMines IC 9039, 1985, 53 pp. These enchanced drilling rates were observed upon the addition of chemicals as well as surfactants; however, favorable results that occurred on the laboratory scale failed to materialize on larger scales. As a result, industrial drillers have ignored these observations and used drilling fluids or muds of the barite type to facilitate deep rock penetration.
Furthermore, laboratory results were found to be very sensitive to the batch of distilled/deionized water used. For a given batch of water, the drilling data is reasonably reproducible and the data trends remain the same from one batch to another batch of distilled/deionized water. However, trace metals present in the distilled/deionized water, such as copper and aluminum were found to exert unpredictable effects on the base-line drilling results.
The present invention provides a means for enhancing drilling rates while also prolonging the bit life at constant applied mechanical stress during drilling operations. This is accomplished by virtue of the invention's discovery that enhanced drilling rates are a function of the rock surface condition, and that, if the rock surface condition is maintained at zero point charge, (ZPC), regardless of the salt type or concentration or water source, enhanced drilling rates coupled with prolongation of the bit life are attained.